3 Phase Shop Power - To Make or Buy??

[reggie_obe]

Before you pull the trigger, check with the utility to see if they are going to hit you with: minimum billing regardless of use; demand metering.

If you're not running any CNC's or sensitive electronics on the three phase, you can probably continue to run your shop without utility three phase. You've learned that you can just start another (unloaded) machine to add to your RPC capacity. No need to have a 25hp RPC running all the time for a 5hp load.

[Wanna-Be]

My present consumption with both my shop and home on the same meter satisfies their min. requirements, since I heat a my home with a head pump or electric heat when it really get too cold. My shop has a waste oil boiler but craps out frequently and I have to keep electric heaters on or dehumidifiyer going to keep machines from flash rusting (can't always get oil in all machined surfaces).
The cost per KwHr isn't that much but the extra $40/mo for "equipt. service fee" does give me some concern and I may end up going to as larger 3phase converter or maybe a smaller and a large one and be selective depending on the load. Both be started and feed the same 3 phase bus system, just as you suggest with the unloaded machine.

Along this line of thought, I have been think, rather than mess with start capacitor on several large rotary motors, I could put this small fractional hp 3 phase motor on the buss and equip it with appropriate start capacitor to "excite" the wild phase on the three phase buss. Should be enough to get either of the larger rotary converter motors rolling. Kind of a Pony motor for the wild leg, so to speak.

Just thinking out loud!!

Steve

[BadDog]

Yep,, that works. My 5/10/15 had start circuit only on the 5HP. It could start the 10, then drop out if I desired.